1. Field of the Invention
The present invention relates to a length-adjustable temple for eyeglasses capable of fitting a concavity inside the outer periphery of an ear and having a length adjusting function.
2. Related Art
General eyeglasses are adapted to be worn by engaging substantially L-shaped earpieces of eyeglass temples provided at the distal portion thereof with ears. However, in the case of presbyopia spectacles, which are used temporarily for reading newspapers or magazines, the wearer tends to choose eyeglasses having a compact front frame. This is not only because of convenience of portability, but also because it is not necessary to use large sized lenses for the temporary use. However, even when the size of the front frame is small, it is still impossible to downsize the eyeglasses entirely unless the length of the temples, which extend from the front frame to engage the ears, is reduced.
An “Eyeglass Temple” is known with JP-U4-50818 in which the length of the temples is shortened by providing engaging portions to be engaged with the concavities inside the outer peripheries of the ears at the distal portions of the temples to reduce the entire size of the eyeglasses in a state in which the temples are folded.
However, since the shape of human beings' ears varies from person to person, the engaging portions can hardly be engaged with the concavities inside the outer peripheries of the ears only by forming the engaging portions at the distal portions of the temples in many cases. If they are forced to engage, the wearer might feel pain, or in some cases, the eyeglasses might fall off. In the above-described document, there is also disclosed an embodiment in which the entire temple is formed of a spring member. However, since the temple formed of a spring member tends to cause overall flexible deformation, the fitting pressure applied on the concavity is too small to give comfortable feeling of fitness to the wearer when he/she wears the eyeglasses and, in addition, it is apt to fall off easily.
In order to fit eyeglasses to the wearer's face, the entire length of the temple is normally regulated by adjusting the bending degree of the earpieces. In the related art, a pair of eyeglasses provided with a temple length adjusting mechanism for facilitating adjustment of the length of the temples is known (JP-A-7-270725, JP-A-9-281446).
JP-A-7-270725 discloses an elastic structure of a temple, in which elasticity is provided to the temples by fitting coil springs over the outer peripheries of the distal portions of the temples, fixing an end of each coil spring to the distal end of each temple, forming a hollow vacancy inside the earpiece, fixing the other end of the coil spring to an inner periphery of the hollow vacancy of the earpiece, and utilizing the hollow vacancy in the earpiece as a joint member.
JP-A-9-281446 discloses an eyeglass temple including an elastic temple, a rotatable temple, and a base temple, in which the rotatable temple formed into a square tube and the elastic temple formed into a square shaft are overlapped so as to allow the elastic temple to slide freely within the rotatable temple, and an elastic spring is interposed at the overlapped area to provide free elasticity to the elastic temple.
However, with such a length adjusting mechanism using the spring, since adjustment of the length is dependent entirely on elasticity of the spring, the adjusting length is not static, and hence it is subjected to instability. In other words, when adjustment is made to increase the length of temple to a large extent, the spring is pulled with a strong force and hence a stress exerted on the ear increases correspondingly, which may cause pain on the wearer's ears. Under such circumstances, it is difficult to make the temples to fit adequately the wearer's ears, and the adjustable width is limited. Furthermore, the thickness of the temple increases inevitably with the provision of the spring, which may impair the appearance as an eyeglass frame. In other words, it is not suitable to satisfy the recent demand for slim eyeglass frames.
As shown in FIG. 14, a length adjusting mechanism employing a screw mechanism is also known. The length of the temple can be elastically adjusted by rotating a distal temple member (b) with respect to a proximal temple member (a) connected to the front member. The length can be adjusted on the basis of pitch distance of the screw, and is locked at the predetermined length by tightening a lock nut (c). However, the temple member (b) cannot be completely fixed simply by tightening the lock nut (c) and, the direction of the earpiece fitted to the distal portion may change with a small amount of rotation of the temple member (b), whereby it cannot be engaged with the ear any longer.